Score : $400$ points

问题描述

给定一个包含 $N$ 个正整数的序列 $A=(a_1,\ldots,a_N)$。

从 $A$ 中选择一个或多个项有 $(2^N-1)$ 种方式。其中有多少种方式可以使得所选项的平均值为整数？请计算该数量对 $998244353$ 取模的结果。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

You are given a sequence of positive integers $A=(a_1,\ldots,a_N)$ of length $N$.
There are $(2^N-1)$ ways to choose one or more terms of $A$. How many of them have an integer-valued average? Find the count modulo $998244353$.

Constraints

• $1 \leq N \leq 100$
• $1 \leq a_i \leq 10^9$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$N$

$a_1$ $\ldots$ $a_N$

Output

Print the answer.

Sample Input 1

3
2 6 2

Sample Output 1

6

For each way to choose terms of $A$, the average is obtained as follows:

• If just $a_1$ is chosen, the average is $\frac{a_1}{1}=\frac{2}{1} = 2$, which is an integer.

• If just $a_2$ is chosen, the average is $\frac{a_2}{1}=\frac{6}{1} = 6$, which is an integer.

• If just $a_3$ is chosen, the average is $\frac{a_3}{1}=\frac{2}{1} = 2$, which is an integer.

• If $a_1$ and $a_2$ are chosen, the average is $\frac{a_1+a_2}{2}=\frac{2+6}{2} = 4$, which is an integer.

• If $a_1$ and $a_3$ are chosen, the average is $\frac{a_1+a_3}{2}=\frac{2+2}{2} = 2$, which is an integer.

• If $a_2$ and $a_3$ are chosen, the average is $\frac{a_2+a_3}{2}=\frac{6+2}{2} = 4$, which is an integer.

• If $a_1$, $a_2$, and $a_3$ are chosen, the average is $\frac{a_1+a_2+a_3}{3}=\frac{2+6+2}{3} = \frac{10}{3}$, which is not an integer.

Therefore, $6$ ways satisfy the condition.

Sample Input 2

5
5 5 5 5 5

Sample Output 2

31

Regardless of the choice of one or more terms of $A$, the average equals $5$.

update @ 2024/3/10 11:06:03